Method for producing a hearing protection cup, and tool used for its production

ABSTRACT

Tool for injection-molding a hearing protection cup which includes a curved shell with an opening for receiving an ear, and a washer which extends around the opening and is connected to the edge thereof. The washer projects inward across the opening along at least two opposite sides thereof and is intended to support a sealing and comfort ring which is intended to rest against the head. The tool includes a common mold cavity intended to produce the shell and the washer in one piece, and an insert which can be introduced into this mold cavity for forming the inner surfaces of the shell and of the washer. The insert is divided into at least three portions by means of dividing planes which extend in the same principal direction as the opposite sides of the opening. The invention also relates to a method for producing a hearing protection cup, and to a hearing protection cup produced using the method.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for producing a hearingprotection cup comprising a curved shell with an opening for receivingan ear and with a washer which extends around said opening, is connectedto the edge thereof and projects inward across the opening along atleast two opposite sides thereof, and which washer is intended tosupport a sealing and comfort ring which is intended to rest against thehead.

[0002] The invention also relates to a tool for injection-molding ahearing protection cup by using this method.

BACKGROUND TO THE INVENTION

[0003] All product development is aimed in principle at reducingproduction costs and at achieving a higher-quality product. This appliesto a very great extent to products of the hearing protection type. Ananalysis of the hearing protections currently available on the marketshows that all the products follow certain common design solutions. Itcan be stated, for example, that all hearing protections of the cup typecomprise two cups, each with a washer which extends around its openingand which is intended to support a sealing and comfort ring intended torest against the head. The cups are either mounted in a frame or inseparate holders intended to be fitted on a safety helmet.

[0004] Each cup and washer is produced by injection-molding of suitableplastic material in the form of two separate components, which arejoined together in a later assembly step. They can be joined together indifferent ways, e.g. by adhesive bonding, ultrasound welding, or usingsnap-fit connections. The use of two production steps and a specialassembly step results in higher production costs than would be the caseif the production could take place in a single step, and it can resultin a faulty product with poor fit between washer and cup, which canlead, for example, to sound getting through.

[0005] However, in a hearing protection cup of the abovementioned type,the washer intended for the sealing and comfort ring generally projectsinward across the opening, from its edge formed by the shell of the cup.This means that the hollow space in the cup under the washer cannot beformed with a conventional insert since the latter, after a moldingoperation, cannot be removed again from the tool.

OBJECTS OF THE INVENTION

[0006] One object of the present invention is to make available a methodfor injection-molding of hearing protection cups in which theabovementioned problems are solved, so that it is possible toinjection-mold a cup with an integrated washer in a single operation.

[0007] Another object is to make available a tool allowing a hearingprotection cup with an integrated washer to be injection-molded in asingle operation.

[0008] The invention is based on the realization that the above aims canbe achieved by using a molding tool in which the insert which forms theinner surfaces of the hearing protection cup and of the washer isdivisible. The shape of the cup is thus expediently modified so that thewasher projects inward across the opening of the cup only along twoopposite sides, while it projects outward from the outside of the shellalong the remaining parts of the opening.

[0009] The special characteristic of a method of the type specified inthe first paragraph is that the shell and washer of the cup are producedin one piece by injection-molding of a plastic material in a moldingtool with an insert which is divided into at least three portions, thedividing planes between these portions extending in the same principaldirection as said opposite sides of said opening.

[0010] This method considerably reduces the production costs, becausefewer parts need to be produced and handled in the production process,and at the same time it eliminates the need for a separate step ofjoining together the cup and washer, which is often time-consuming. Inaddition, it eliminates any risk of sound getting through between washerand cup, as these are integrated into a single component.

[0011] It is preferable to use a three-part insert with a centralportion and two side portions situated either side of the latter. Aftera molding operation, the central portion of the insert is first removed,after which the side portions are pushed in sequence or simultaneouslyinto the hollow space after the central portion of the insert and areremoved from the tool. Such a production method can be easily automatedand results in reduced production costs.

[0012] The hearing protection cup preferably has a substantially ovalopening, the washer projecting inward across the opening along part ofthe opposite long sides of the oval opening, while it projects outwardfrom the outside of the shell along opposite end portions of theopening. The central portion of the three-part insert is used forforming the edge of the opening only along the opposite end portions ofthe opening where the washer does not project inward across the opening.

[0013] Other features of a production method according to the inventionand of a tool for injection-molding a hearing protection cup are set outin the attached patent claims.

[0014] The invention will now be described in more detail below withreference to the embodiments shown by way of example in the attacheddrawings.

BRIEF DESCRIPTION OF THE FIGURES

[0015]FIGS. 1 and 2 are perspective views of a hearing protection cupaccording to the present invention.

[0016]FIG. 3 is a perspective view of the shell of a hearing protectioncup according to FIGS. 1 and 2.

[0017]FIG. 4 shows a cross section through a hearing protection cupaccording to the invention.

[0018]FIG. 5 shows a longitudinal section through a hearing protectioncup according to the invention.

[0019]FIG. 6 shows a cross section through a schematically depicted toolfor injection-molding a hearing protection cup according to theinvention.

[0020]FIG. 7 shows part of a longitudinal section through the toolaccording to FIG. 6.

[0021]FIG. 8 illustrates the design of a tool insert used in accordancewith FIGS. 6 and 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The hearing protection cup 1 according to FIGS. 1 and 2 comprisesa curved shell 2 of suitable plastic material with connection members 3,4 to permit fitting on a crown frame or directly on a safety helmet. Anelastic and soft sealing and comfort ring 5 is arranged on that side ofthe cup facing toward the head. Inside the cup shell 2 there is asound-damping foamed plastic material 6.

[0023] The comfort ring 5 is supported by a washer 7, 8 (see FIG. 3)which is arranged around the oval opening of the cup and projects inwardacross the opening along opposite long sides of the cup, whereas itprojects slightly outward from the curved shell of the cup 2 at its endportions in order to form a washer with a sufficient mounting surfacearound the whole opening. To obtain the outwardly projecting portions 8at the ends of the cup, the shell of the cup 2 is modified so that ithas a straight portion 9 at the short ends. The straight portions 9adjoin the inner surface of the cup in such a way that there is noundercut at these end portions. The washer 7 projects inward across theopening along the remaining part of the opening of the cup.

[0024] Reference number 10 indicates two flanges which project inwardacross the washer 7, these flanges being used to fit the comfort ring 5so that the latter is held securely on the cup 2, as is shownschematically in the cross section in FIG. 4. The comfort ring 5 is forthis reason preferably provided with a stiffened base plate which can bedriven into the groove 11 formed between the flanges 10 and the washer7.

[0025] It will be seen from the longitudinal section in FIG. 5 that, atthe straight end portions 9, the shell of the cup 2 does not have anyundercut portion, for which reason these end surfaces can be formed withan insert which, after molding, can be easily removed from the inside ofthe cup. By contrast, the longitudinal edge portions of the cup with thewasher 7 projecting inward across the opening cannot be formed with aone-piece insert.

[0026] According to the present invention, this problem is solved byusing an insert which is divided in three in the longitudinal direction,as can be seen from the schematic cross section through a molding tool12 in FIG. 6. The molding tool 12 comprises an outer mold and an insertwhich in the longitudinal direction is divided into a central portion 13and two side portions 14 situated either side of the latter. The centralportion 13 has a width which does not exceed the width of the straightportion 9 without undercut at the end portions of the cup. This centralportion 13 of the insert with straight end portions 15 can be liftedstraight up after a molding operation. This possibility can also be seenfrom FIG. 7 which is a part of a longitudinal section through one endportion of the insert 13 and shows that there is no undercut at the endsof the central portion 13.

[0027] Those parts of the washer 7 extending along the long sides of theshell of the cup 2 are in the form of flanges which are integrated withthe shell. According to what has been stated above, these flanges andthe other flanges 10 lying over them cannot be molded by means of aninsert which is to be lifted straight up after a molding operation. Forthis reason, the side portions 14 of the insert are designed in such away that, when the central portion 13 has been removed, they can bepushed together and thereafter lifted straight up (see FIG. 8). This ismade possible by the fact that the engagement of the flanges 7 and 10with the insert is released. If the engagement of the flanges 7 with theinsert is very deep or the central portion 13 of the insert is verynarrow, then, once the central portion 13 has been removed, it isalternatively possible for the one side portion 15 first to be pushedsideways and lifted up, and thereafter the second one.

[0028] By means of a modification of the technique described above, itis possible to produce cup shells in which the end portions are alsodesigned with undercut portions. In this case the central portion 13 ofthe insert is designed with two transverse dividing planes, so that onecan first remove the middle part of the central portion and then pushits side parts together, after which these side parts can be removed.Thereafter, the side portions of the insert can then be removed, as hasbeen described above.

[0029] The invention has been described above in connection with thedesign of a hearing protection cup shown in the drawings. However, theprinciple according to the invention can be used for producing cups orthe like with other shapes which have undercut portions.

1. A method for producing a hearing protection cup which comprises acurved shell with an opening for receiving an ear, and a washer whichextends around the opening and is connected to the edge thereof, andwhich washer projects inward across the opening along at least twoopposite sides thereof and is intended to support a sealing and comfortring which is intended to rest against the head, characterized in thatthe shell and the washer are produced in one piece by injection-moldingof a plastic material in a molding tool with an insert which is dividedinto at least three portions, the dividing planes between these portionsextending in the same principal direction as said opposite sides of saidopening.
 2. The method as claimed in claim 1, characterized in that athree-part insert is used which has a central portion and two sideportions situated either side of the latter, and in that, after amolding operation, the central portion of the insert is first removed,after which the side portions are pushed in sequence or simultaneouslyinto the hollow space after the central portion of the insert and areremoved from the tool.
 3. The method as claimed in claim 2 for producinga hearing protection cup with a substantially oval opening, and in whichsaid washer projects inward across the opening along part of theopposite long sides of the oval opening, while it projects outward fromthe outside of the shell along the opposite end portions of the opening,characterized in that a three-part insert is used with a central portionwhich forms the edge of the opening only along said opposite endportions of the opening where the washer does not project inward acrossthe opening.
 4. The method as claimed in claim 1 for producing a hearingprotection cup in which the washer extending around the opening projectsinward across the opening along the entire periphery thereof,characterized in that a molding tool is used with an insert having threelongitudinal dividing planes, and in which the central portion formed bythese dividing planes is divided into three parts by means of twotransverse dividing planes, and in that, after a molding operation, themiddle part of the central portion is first removed, thereafter the sideparts of the central portion, and finally the two side portions.
 5. Atool for injection-molding a hearing protection cup which comprises acurved shell (2) with an opening for receiving an ear, and a washer (7,8) which extends around the opening and is connected to the edgethereof, and which washer projects inward across the opening along atleast two opposite sides thereof and is intended to support a sealingand comfort ring (5) which is intended to rest against the head,characterized in that it comprises a common molding cavity intended forproducing the shell (2) and the washer (7, 8) in one piece, with aninsert (13, 14) which is intended for forming the inner surfaces of theshell and of the washer and is divided into at least three portions, andin that the dividing planes of the insert extend in the same principaldirection as said opposite sides of said opening.
 6. The tool as claimedin claim 5, characterized in that the insert is in three parts andcomprises a central portion and two side portions (14) situated eitherside of the latter, in that the central portion (13) of the insert canbe separated from the side portions (14), so that, after a moldingoperation, the central portion of the insert can be removed first, afterwhich the side portions can be pushed in sequence or simultaneously intothe hollow space after the central portion of the insert and can beremoved from the mold cavity.
 7. The tool as claimed in claim 6 forproducing a hearing protection cup with a substantially oval opening,and in which said washer (7, 8) projects inward across the opening alongpart of the opposite long sides of the oval opening, while it projectsoutward from the outside of the shell (2) along opposite end portions ofthe opening, characterized in that the central portion (13) of thethree-part insert is intended to form the edge (9) of the opening onlyalong said opposite end portions of the opening where the washer (8)does not project inward across the opening.
 8. The tool as claimed inclaim 7 for producing a hearing protection cup with a substantially ovalopening, in which opposite end portions of the opening are substantiallystraight, characterized in that the central portion (13) of the inserthas end portions (15) which are cut substantially straight.
 9. The toolas claimed in claim 5 for injection-molding a hearing protection cup, inwhich said washer projects inward across the opening along the whole ofits periphery, characterized in that the insert is designed with threelongitudinal dividing planes, in that the central portion (13) formed bythese dividing planes is divided into three parts by means of twotransverse dividing planes, so that, after a molding operation, themiddle part of the central portion can first be removed, thereafter theside parts of the central portion, and finally both side portions of theinsert.
 10. A hearing protection cup comprising a curved shell (2) withan opening for receiving an ear, and with a washer (7, 8) which extendsaround the opening and is connected to the edge thereof and is intendedto support a sealing and comfort ring (5) intended to rest against thehead, characterized in that the washer projects inward across theopening only along two opposite sides thereof, and in that the shell (2)and the washer (7, 8) are produced in one piece in a commoninjection-molding operation.